Imides from alkenes

In 1975, van der Baan and Bickelhaupt reported the synthesis of imide 37 from pyridone 34 as an approach to the hetisine alkaloids, using an intramolecular alkylation as the key step (Scheme 1.3) [23]. Beginning with pyridone 34, alkylation with sodium hydride/allyl bromide followed by a thermal [3,3] Claisen rearrangement gave alkene 35. Next, formation of the bromohydrin with A -bi omosuccinimide and subsequent protection of the resulting alcohol as the tetrahydropyranyl (THP) ether produced bromide 36, which was then cyclized in an intramolecular fashion to give tricylic 37. 

Scheme 12. Proposed mechanism leading to the allylic imide observed as a side product in the allylic oxidation of alkenes in nitrile solvents. [Adapted from (120).]...

From the results of the 1,3-diene addition reaction, the metal-catalyzed reaction of unactivated alkenes was examined, and it was found that the palladium complex effectively catalyzed the a rt-Markovnikov addition of triarylphosphines and bis(trifluoromethanesulfonyl)imide (Tf2NH).24... 

Method B The alkene (39 mmol) in MeCN (30 ml) is refluxed for 3 h with the 1 1 N-bromosuccinimide TBA-Br complex (10 g, 20 mmol), prepared by refluxing the imide and TBA-Br in MeCN. The mixture is cooled to room temperature and the solvent removed under reduced pressure. The dibromoalkane is purified by chromatography from silica. 

The reactions of 1,2,3-triazolium 1-imide (277) with a range of alkene and alkyne dipolarophiles give rise to a variety of new ring systems (Scheme 54). Compounds (276) and (278) are obtained from (277) by reaction with acrylonitrile and DMAD, respectively. These reactions are tandem 1,3-dipolar (endo) cycloadditions and sigmatropic rearrangements which are regio- and stereospecific <90JCS(Pl)2537>. Kinetic and mechanistic studies show that these reactions are dipole-HOMO controlled. The second-order rate constants are insensitive to solvent polarity, the reaction indicates... 

Numerous examples involving the preparation of tetrahydrothiophenes via [3 + 2] cycloaddition of thiocarbonyl ylides with electron-poor alkenes have been reported. Thiobenzophenone (5)-methylide (16), generated from 2,5-dihydro-1,3,4-thiadiazole (15) and analogous compounds, react with maleic anhydride, N-substituted maleic imide, maleates, fumarates, and fumaronitrile at —45°C (28,91,93,98,128,129). Similar reactions with adamantanethione (5)-methylide (52) and 2,2,4,4-tetramethyl-3-thioxocyclobutanone (5)-methylide (69) occur at ca. +45°C and, generally, the products of type 70 were obtained in high yield (36,94,97,130) (Scheme 5.25). Reaction with ( )- and (Z)-configured dipolaro-philes stereospecifically afford trans and cis configured adducts. 

The first successful generation and trapping of isomiinchnones using this strategy was described independently by Maier et al. (36,37) and Padwa et al. (38,39). Maier and Evertz (36) were the first workers to report the intramolecular dipolar cycloaddition of isomiinchnones to alkenes, the reaction that Padwa would later exploit so spectacularly. Thus, diazo imide 62 was readily prepared from... 

Imidates, generated from secondary amides, are treated with trimethylsilyhnethyl triflate to give an azomethine ylid which reacts with electron-poor alkenes and acetylenes, yielding A2-pyrroline and pyrrole derivatives.54 Similar transformations are conducted from thioamides (vide infra). 

Electronically excited carbonyl chromophores in ketones, aldehydes, amides, imides, or electron-deficient aromatic compounds may act as electron acceptors (A) versus alkenes, amines, carboxylates, carboxamides, and thioethers (D, donors). In addition, PET processes can also occur from aromatic rings with electron-donating groups to chloroacetamides. These reactions can be versatile procedures for the synthesis of nitrogen-containing heterocyclic compounds with six-membered (or larger) rings [2],... 

Phosphoranes and phosphonate derived carbanions are also known to react with carbonyl compounds other than aldehydes and ketones, in reactions often referred to as non-classical Wittig reactions.35 Wittig olefination products can be obtained from the reaction of esters, anhydrides and some amides and imides with a range of stabilized and reactive phosphoranes. The reaction of stabilized and semi-stabilized phosphoranes with esters gives alkenes (Scheme 7). However, non-stabilized phosphoranes, such as methylenetriphenylphosphorane, tend to give P-keto phosphoranes on reaction with esters (Scheme 7)—the careful choice of the reaction conditions can also permit the preparation of the alkene in these reactions. 

The most widely used and, presumably, the most chemoselective reagents for the epoxidation of nucleophilic C—C double bonds are the peroxycarboxylic acids (see Houben-Weyl, Vol. IV/ 1 a, p 184, Vol. Vl/3, p 385, Vol. E13/2, p 1258). Using chloroform as solvent, epoxidation rates are particularly high79. Reactive or acid/base sensitive epoxides can often be obtained with dimethyldioxirane (see Houben-Weyl, Vol. R13/2, p 1256 and references 15, 16, 87-90), peracid imides (see Houben-Weyl, Vol. IV/1 a, p 205, Vol. VI/3, p 401, Vol. E13/2, p 1276) (prepared in situ from nitriles and hydrogen peroxide), hydroperoxy acetals (see Houben-Weyl, Vol. El3/2, p 1253) or peroxycarbonic acid derivatives (see Houben-Weyl, Vol. IV/la, p 209 and references 17-19) as oxidants. For less reactive alkenes, potassium hydrogen persulfate is a readily available reagent for direct epoxidation20. 

In the reaction of alkenes with 4-substituted 3//-l,2,4-triazole-3,5(4//)-diones (13), the ene products, the diazetidines, the vinyl hydrazine derivatives, and rearrangement products, all derive from a common intermediate 14 which is thought to be an aziridinium imide or a 1,4-zwitter-ionic intermediate20 23. The intermediate can be trapped by methanol or acetone20 24. 

The photolytic cleavage of alkyl aryl sulfoxides has been shown to occur via initial C—S bond homolysis, in accordance with the common mechanistic assumption. Secondary and tertiary alkyl groups show high chemoselectivity for alkyl C—S cleavage. Uniquely, alkene products have been isolated, formed by disproportionation of the initial alkyl radical, with the formation of benzaldehyde and racemization of primary alkyl compounds. An investigation into the photochemical conversion of N-propylsulfobenzoic imides into amides in various solvents revealed a solvent dependence of the observed mechanism. In ethanol, sulfur dioxide extension forms a biradical which abstracts a hydrogen atom from the solvent, whereas in aromatic solvents biradical formation by a single electron transfer is implicated. The photolysis and thermolysis of l,9-bis(alkylthio)dibenzothiophenes and /7-aminophenyl disulfide have been studied. 

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